Liquid crystal display and backlight module thereof

ABSTRACT

A backlight module includes a reflection sheet and a film structure disposed above the reflection sheet with a gap therebetween. A light source is disposed in the gap between the reflection sheet and the film structure so as to provide light. The film structure includes a first region for reflecting light incident thereupon from the light source and the reflection sheet, and a plurality of second regions for transmitting at least partially light incident thereupon from the light source and the reflection sheet.

This application claims the benefit of Taiwan application Serial No.96112988, filed Apr. 13, 2007, the entirety of which is incorporatedherein by reference.

BACKGROUND

1. Technical Field

The disclosure relates to a display and a backlight module thereof, andmore particularly, to a liquid crystal display and a backlight modulethereof.

2. Description of Related Art

With the progress in modern visual information technologies, the liquidcrystal display (LCD) has been widely applied to the display screen ofconsumer electronic products, such as mobile phones, notebook personalcomputers, personal computers (PCs) and personal digital assistants(PDAs). However, as the LCD panel in an LCD device is incapable ofemitting light, a backlight module is required to be disposed under theLCD panel to provide the light source for the LCD panel, thus enablingthe LCD panel to display images.

Generally, backlight modules are divided into direct type backlightmodules and side incident type backlight modules. The direct typebacklight modules are usually applied to large-sized LCDs, whereas theside incident type backlight modules are usually adopted in small-sizedLCDs.

FIG. 1 is a schematic view of a conventional side incident backlightmodule. Referring to FIG. 1, a side incident type backlight module 100includes a light guide plate (LGP) 130, a plurality of cold cathodefluorescent lamps 120, a lamp holder 110 and an optical film 140. Thelight guide plate 130 has an incident surface 114 and an emittingsurface 116. The cold cathode fluorescent lamps 120 are disposedadjacent to the incident surface 114 of the light guide plate 130 andinside the lamp holder 110. Moreover, the optical film 140 is disposedon the emitting surface 116 of the light guide plate 130. Light emittedfrom the cold cathode fluorescent lamps 120 would either directlypropagate towards the light guide plate 130, or the light would be firstreflected by the lamp holder 110, then propagate towards the light guideplate 130 and finally emit from the emitting surface 116 of the lightguide plate 130. The function of the light guide plate 130 is to convertlight emitted by the cold cathode fluorescent lamps 120 from a linesource to a surface source.

Since a thick and heavy light guide plate 130 is adopted in the sideincident type backlight module 100, the side incident type backlightmodule 100 has the problem of overweight. Furthermore, if the sideincident type backlight module 100 is applied to large-sized LCDs, thedisadvantages of low yield rate and tendency to warping in large-sizedlight guide plates 130 would arise.

SUMMARY OF THE INVENTION

There is a need for a backlight module and/or a liquid crystal display(LCD) which is flexible and does not require a light guide plate or adiffusion plate.

In an aspect, the invention provides a backlight module including areflection sheet, a first reflective type polarizer, a light source, aretarder and a second reflective type polarizer. The first reflectivetype polarizer is disposed above the reflection sheet with a gaptherebetween. The light source is disposed in the gap between thereflection sheet and the first reflective type polarizer to providelight. The retarder is disposed on the first reflective type polarizerand has a plurality of retarding regions and a non-retarding region. Thesecond reflective type polarizer is disposed on the retarder. Lightprovided by the light source penetrates the second reflective typepolarizer through the functioning of the retarding regions.

According to one embodiment, the first reflective type polarizer and thesecond reflective type polarizer are linear polarizers. Linearpolarization directions of the first reflective type polarizer and thesecond reflective type polarizer are perpendicular to each other.

According to one embodiment, the first reflective type polarizer and thesecond reflective type polarizer are circular polarizers. Circularpolarization directions of the first reflective type polarizer and thesecond reflective type polarizer are opposite to each other. Inaddition, the backlight module may further include a ¼ wavelengthretarder disposed on the second reflective type polarizer.

According to one embodiment, the light source of the backlight module islocated along an edge of the reflection sheet and emits light towards acentral region of the reflection sheet. Additionally, the backlightmodule may further include a lens disposed on a light-emitting path ofthe light source.

According to one embodiment, the light source includes a plurality oflight-emitting elements distributed evenly on the reflection sheet.

According to one embodiment, the backlight module further includes aplurality of fasteners for fixing relative positions of the reflectionsheet, the first reflective type polarizer, the retarder and the secondreflective polarizer. The reflection sheet, the first reflective typepolarizer, the retarder and the second reflective type polarizer have aplurality of through holes respectively. The fasteners run through thethrough holes to fasten the reflection sheet, the first reflective typepolarizer, the retarder and the second reflective type polarizer. Alargest dimension of at least one of the through holes is larger than alargest external diameter of the respective fasteners.

According to one embodiment, the reflection sheet, the first reflectivetype polarizer, the retarder and the second reflective type polarizerare flexible.

In one embodiment, the backlight module further includes a supportdisposed between the reflection sheet and the first reflective typepolarizer so as to maintain the gap therebetween. The backlight modulemay further include a transparent support plate disposed between thefirst reflective type polarizer and the support.

In one embodiment, the retarder is a ½ wavelength retarder.

In one embodiment, a total area of the retarding regions per unit areaof the retarder increases as the retarding regions are farther away fromthe light source.

In another aspect, the invention further provides a backlight moduleincluding a reflection sheet, a selective reflection sheet and a lightsource. The selective reflection sheet is disposed above the reflectionsheet with a gap therebetween, and has a plurality of transparentregions and a reflective region. The light source is disposed in the gapbetween the reflection sheet and the selective reflection sheet so as toprovide light.

In one embodiment, a total area of the transparent regions per unit areaof the selective reflection sheet increases as the transparent regionare farther away from the light source.

In a further aspect, the invention further provides a backlight moduleincluding a reflection sheet, a film structure disposed above thereflection sheet with a gap therebetween, and a light source disposed inthe gap between the reflection sheet and the film structure so as toprovide light. The film structure includes a first region for reflectinglight incident thereupon from the light source and the reflection sheet,and a plurality of second regions for transmitting at least partiallylight incident thereupon from the light source and the reflection sheet.

In one embodiment, a total area of the second regions per unit area ofthe film structure increases as the second regions are farther away fromthe light source.

In another embodiment, the backlight module is a side incident typebacklight module wherein the light source is located along an edge ofthe reflection sheet and emits light towards a central region of thereflection sheet, and the second regions are distributed on the filmstructure such that a surface source with uniform luminance is providedat a top side of the film structure.

In yet a further aspect, the invention further provides an LCD includingan LCD panel and a backlight module of any of the types disclosed above.The backlight module is disposed under the LCD panel.

Additional aspects and advantages of the disclosed embodiments are setforth in part in the description which follows, and in part are apparentfrom the description, or may be learned by practice of the disclosedembodiments. The aspects and advantages of the disclosed embodiments mayalso be realized and attained by means of the instrumentalities andcombinations particularly pointed out in the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a furtherunderstanding of embodiments of the invention, and are incorporated inand constitute a part of this specification.

FIG. 1 illustrates a schematic view of a conventional side incident typebacklight module.

FIG. 2 illustrates a schematic cross-sectional view of a backlightmodule according to one embodiment of the present invention.

FIG. 2B illustrates a three-dimensional schematic view of the backlightmodule of FIG. 2A.

FIG. 2C is a schematic view illustrating the relative positions of thefilms in the backlight module of FIG. 2A.

FIG. 2D is a see-through perspective view similar to FIG. 2B.

FIG. 2E illustrates a schematic view of the warped backlight module ofFIG. 2A.

FIG. 3 is a schematic view illustrating the relative positions of thefilms in a backlight module according to another embodiment of theinvention.

FIG. 4 illustrates a schematic cross-sectional view of a backlightmodule according to yet another embodiment of the invention.

FIG. 5 illustrates a schematic cross-sectional view of a backlightmodule according to still another embodiment of the invention.

FIG. 6 illustrates a schematic cross-sectional view of a backlightmodule according to another embodiment of the invention.

FIG. 7A illustrates a schematic cross-sectional view of a backlightmodule according to one embodiment of the invention.

FIG. 7B is a schematic view illustrating the relative positions of thefilms in the backlight module of FIG. 7A.

FIG. 8 illustrates a schematic cross-sectional view of a backlightmodule according to another embodiment of the invention.

FIG. 9 illustrates a cross-sectional view of a backlight module having atransparent support plate according to another embodiment of theinvention.

FIG. 10 illustrates a schematic cross-sectional view of a backlightmodule according to yet another embodiment of the invention.

FIG. 11 illustrates a schematic view of an LCD according to oneembodiment of the invention.

FIG. 12 illustrates a schematic view of an LCD according to anotherembodiment of the invention.

DESCRIPTION OF EMBODIMENTS

Reference will now be made in detail to the present embodiments of theinvention, examples of which are illustrated in the accompanyingdrawings. Wherever possible, the same reference numbers are used in thedrawings and the description to refer to the same or like parts.

FIG. 2A illustrates a schematic cross-sectional view of a backlightmodule according to one embodiment of the present invention. FIG. 2Billustrates a three-dimensional schematic view of the backlight moduleof FIG. 2A. Referring to FIGS. 2A and 2B, a backlight module 300includes a reflection sheet 310, a first reflective type polarizer 320,a light source 340, a retarder 350 and a second reflective typepolarizer 360. The first reflective type polarizer 320 is disposed abovethe reflection sheet 310 and a gap 380 is formed therebetween. The lightsource 340 is disposed between the reflection sheet 310 and the firstreflective type polarizer 320 to provide light. The light source 340 ofthe present embodiment is located along an edge of the reflection sheet310 and emits light towards a central region of the reflection sheet310. Furthermore, the light source 340 includes at least onelight-emitting element. The light-emitting element may be a lightemitting diode (LED), a cold cathode fluorescent lamp or other suitablelight sources. The light source 340 including a plurality of lightemitting diodes (LEDs) as shown in FIG. 2B serves as an example herein.The retarder 350 is disposed on the first reflective type polarizer 320.The second reflective type polarizer 360 is disposed on the retarder350. In other words, the retarder 350 is disposed between the firstreflective type polarizer 320 and the second reflective type polarizer360.

In the present embodiment, the backlight module 300 may further includeat least one support 330 disposed between the reflection sheet 310 andthe first reflective type polarizer 320 so as to maintain the gap 380.The supports 330 may be constituted by transparent or reflectivematerials, and the number of the supports 330 may be selected to meetactual needs. Additionally, the backlight module 300 may further includea plurality of fasteners 370 for fixing the relative positions of thereflection sheet 310, the first reflective type polarizer 320, theretarder 350 and the second reflective type polarizer 360. The fasteners370 are located, for example, at corners of the foregoing films as shownin FIG. 2B.

FIG. 2C is a schematic view illustrating the relative positions of thefilms in the backlight module of FIG. 2A. The support(s) and thefasteners of the backlight module are not illustrated in FIG. 2C.Referring to FIGS. 2A and 2C, the retarder 350 has a plurality ofretarding regions 352 and at least one non-retarding region 354. Light Aprovided by the light source 340 penetrates the second reflective typepolarizer 360 through the functioning of the retarding regions 352. Amethod for forming the retarder 350 includes, for example, selectivelyprinting a retarding material on a transparent film. An area printedwith the retarding material defines the retarding region 352, whereas anarea without the retarding material defines the non-retarding region354. In the present embodiment, a total area of the retarding regions352 per unit area on the retarder 350 increases, preferably gradually,as the retarding regions are farther away from the light source 340. Theresult can be achieved by several different designs. For example, asillustrated in FIG. 2C, an area of each of the retarding regions 352gradually increases as the retarding region gets farther away from thelight source 340. Alternatively, the areas of the retarding regions 352are the same, but the number of the retarding regions 352 per unit areagradually increases as the retarding regions are farther away from thelight source 340.

In the embodiment, the second reflective type polarizer 360 and thefirst reflective type polarizer 320 are linear polarizers as shown inFIG. 2C, for example. A linear polarization direction 322 of the firstreflective type polarizer 320 is perpendicular to a linear polarizationdirection 362 of the second reflective type polarizer 360. Moreover, inthe embodiment, the retarder 350 is, for example, a ½ wavelengthretarder, which means the retarding regions 352 are likewise ½wavelength retarding regions, for example. Each retarding region 352 hasa fast axis 352 a and a slow axis (not illustrated), and the fast axis352 a and the slow axis are perpendicular to each other. After passingthrough the retarding regions 352, a phase of the light A whose electricfield is parallel to the slow axis is 180 degrees behind a phase of thelight A whose electric field is parallel to the fast axis 352 a. Thefast axis 352 a is disposed at an angle of 45 degrees with respect tothe linear polarization direction 322 of the first reflective typepolarizer 320 and the linear polarization direction 362 of the secondreflective type polarizer 360. Thus, after a portion of the light Apassing through the first reflective type polarizer 320 penetrates theretarding regions 352, the linear polarization direction of the portionof the light A is rotated 90 degrees and then it passes through thesecond reflective type polarizer 360. However, a portion of the light Apassing through the non-retarding regions 354 does not change its linearpolarization direction, and therefore is reflected by the secondreflective type polarizer 360 and cannot pass through it. The portion ofthe light A reflected by the second reflective type polarizer 360 isreflected by the reflection sheet 310 and thus can be utilized againafter penetrating the retarder 350 and the first reflective typepolarizer 320. Moreover, since the total area of the retarding regions352 per unit area gradually increases as the retarding regions arefarther away from the light source, for the light A penetrating thesecond reflective type polarizer 360, a luminous flux per unit area ofthe light A in regions closer to the light source 340 is approximate toa luminous flux per unit area of the light A in regions farther from thelight source 340. Hence, a surface source of uniform luminance can beobtained.

FIG. 2D is a see-through perspective view similar to FIG. 2B, and FIG.2E is a schematic view of the warped backlight module of FIG. 2A.Referring to FIGS. 2A, 2B, 2D and 2E, in the present embodiment, thereflection sheet 310, the first reflective type polarizer 320, theretarder 350 and the second reflective type polarizer 360 have aplurality of through holes 396 respectively. The fasteners 370 runthrough the through holes 396 to fasten the reflection sheet 310, thefirst reflective type polarizer 320, the retarder 350 and the secondreflective type polarizer 360. All the aforementioned fastened films areflexible, for example. The through holes 396 are divided into a firstthrough hole 396 a and a second through hole 396 b. In FIG. 2B, one ofthe fasteners 370 is removed for showing one through hole 396 a. Alargest dimension B of the second through hole 396 b is larger than alargest external diameter C of the fasteners 370. For example, thesecond through hole 396 b can be fabricated as a slot as shown in FIG.2B. If the backlight module 300 is warped (as illustrated in FIG. 2E),the fasteners 370 may slide along a longitudinal direction of such slot,i.e., the largest dimension B, in the second through hole 396 b. Adiameter D of the first through hole 396 a is approximate to the largestexternal diameter C of the fasteners 370 and ensures a good fasteningeffect of the fasteners 370. With a combination of the first throughhole 396 a, the second through hole 396 b and the fasteners 370, notonly the backlight module 300 is suitable for proper functioning evenwhen it is being warped, but all the films in the backlight module 300can also be well fastened.

According to the aforementioned description, the backlight module 300 ofthe embodiment produces a surface source of uniform luminance by usingthe combination of the reflection sheet 310, the first reflective typepolarizer 320, the retarder 350 and the second reflective type polarizer360, and a thick and heavy light guide plate is not required unlike theconventional side incident type backlight module. Therefore, thebacklight module 300 has the advantages of thinner thickness and lighterweight. Furthermore, the backlight module 300 does not employ anyelements that are difficult to warp, such as a light guide plate or adiffusion plate, so that it can be easily designed as a flexible typebacklight module. In addition, when the backlight module 300 is of alarger size (such as those applied in large-sized LCDs), since it doesnot have a light guide plate, the problems of low yield rate andtendency to warping in large-sized light guide plates can be avoided.

FIG. 3 is a schematic view illustrating relative positions of films in abacklight module according to another embodiment of the invention. Asupport and fasteners of the backlight module are not illustrated inFIG. 3. Referring to FIG. 3, in the present embodiment, a secondreflective type polarizer 360 a and a first reflective type polarizer320 a are circular polarizers. A circular polarization direction 324 ofthe first reflective type polarizer 320 a is opposite to a circularpolarization direction 364 of the second reflective type polarizer 360a. For example, one of the circular polarization directions 324 and 364is clockwise, whereas the other is counterclockwise. Circularpolarization directions of the light A are opposite before and afterpassing through the retarding regions 352. Thus, the light A passingthrough the retarding regions 352 may continue to pass through thesecond reflective type polarizer 360 a. The light A passing through thenon-retarding region 354 is reflected by the second reflective typepolarizer 360 a. A portion of the light A reflected by the secondreflective type polarizer 360 a is reflected by the reflection sheet 310and thus can be utilized again after penetrating the retarder 350 andthe first reflective type polarizer 320 a. Further, a ¼ wavelengthretarder 390 may be disposed on the second reflective type polarizer 360a. The light A coming from the second reflective type polarizer 360 achanges from a circular polarizing state to a linear polarizing stateafter penetrating the ¼ wavelength retarder 390. This feature issuitable for LCD panels whose bright or dark state is determined bywhether linear polarizing light passes through the LCD panels or not,such as the twisted nematic (TN) LCD panel, the in-plane switching (IPS)LCD panel, or the vertical alignment (VA) LCD panel.

FIG. 4 illustrates a schematic cross-sectional view of a backlightmodule according to yet another embodiment of the invention. Referringto both FIGS. 2A and 4, the backlight module 300 a is approximately thesame as a backlight module 300. The difference is that the backlightmodule 300 a further includes a lens 392 disposed on a light-emittingpath of the light source 340. The lens 392 is utilized to control adirection of the light A emitted by the light source 340 so as toimprove the utilization the backlight module 300 a has of the lightsource 340.

FIG. 5 illustrates a schematic cross-sectional view of a backlightmodule according to still another embodiment of the invention. Referringto FIGS. 2A and 5, the backlight module 300 b is approximately the sameas a backlight module 300. The difference is that the backlight module300 b further includes a transparent support plate 394 disposed betweenthe first reflective type polarizer 320 and the support 330 so as toincrease the strength of the backlight module 300 b. The transparentsupport plate 394 is especially suitable for large-sized backlightmodules. The transparent support plate 394 is fabricated using, forexample, a transparent acrylic plate or other transparent materials.

It should be noted that the present invention does not limit the lightsource 340 (referring to FIG. 2A) to be disposed on the edge of thereflection sheet 310 (as in the side incident type backlight module). Inanother embodiment of the invention, as shown in FIG. 6, a light source340 a of a backlight module 300 c includes a plurality of light-emittingelements 342 evenly distributed on the reflection sheet 310 (as in thedirect type backlight module). In the embodiment as shown in FIG. 6, atotal area of the retarding regions 352 per unit area on the retarder350 increases, preferably gradually, as the retarding regions arefarther away from the light-emitting elements 342. Each light-emittingelement 342 is, for example, a light emitting diode (LED) or a coldcathode fluorescent lamp.

FIG. 7A illustrates a schematic cross-sectional view of a backlightmodule according to one embodiment of the invention. FIG. 7B is aschematic view illustrating the relative positions of the films in thebacklight module of FIG. 7A. Referring to FIGS. 7A and 7B, a backlightmodule 400 includes a reflection sheet 410, a selective reflection sheet420 and at least one light source 440. The reflection sheet 410 canreflect light A from the light source 440. The selective reflectionsheet 420 is disposed above the reflection sheet 410 and includes aplurality of transparent regions 422 and at least one reflective region424. The selective reflection sheet 420 and the reflection sheet 410form a gap 460. A method for forming the transparent regions 422 and thereflective region 424 includes, for example, selectively coating areflective material (such as a metal or metals) on a transparent film.An area coated with the reflective material defines the reflectiveregion 424, whereas an area not coated with the reflective materialdefines the transparent region 422. The light source 440 is disposed inthe gap 460 between the reflection sheet 410 and the selectivereflection sheet 420 to provide light A. The light source 440 is locatedalong an edge of the reflection sheet 410 and emits light towards acentral region of the reflection sheet 410, for example. Furthermore,the light source 440 includes at least one light-emitting element, andthe light-emitting element may be an LED, a cold cathode fluorescentlamp or other suitable light sources.

In the present embodiment, the backlight module 400 further includes atleast one support 430 disposed between the reflection sheet 410 and theselective reflection sheet 420 to maintain the gap 460. The support 430is constituted, for example, by transparent or reflective materials.Moreover, the backlight module 400 further includes a plurality offasteners 450 for fixing the relative positions of the reflection sheet410 and the selective reflection sheet 420. The fasteners 450 are, forexample, located at corners of the films.

A portion of the light A emitted by the light source 440 passes throughthe transparent regions 422. Another portion of the light A reflected bythe reflective regions 424 is then reflected by the reflection sheet 410to be utilized again. In the embodiment, a total area of the transparentregions 422 per unit area increases, preferably gradually, as thetransparent regions are farther away from the light source 440.Positions and sizes of the transparent regions 422 and a number of suchtransparent regions per unit areas are designed in the same method asthe retarding regions 352 (referring to FIG. 2C) of the backlight module300. Hence, the backlight module 400 can provide a surface source ofuniform luminance.

In addition, the reflection sheet 410 and the selective reflection sheet420 have a plurality of through holes 480 respectively. The fasteners450 run through the through holes 480 to fasten the reflection sheet 410and the selective reflection sheet 420. Further, the reflection sheet410 and the selective reflection sheet 420 may be flexible. Shapes anddimensions/diameters of the through holes 480 and an external diameterof the fastener 450 are similar to those of the through holes 396 andthe external diameter C of the fasteners 370 in the backlight module 300(referring to both FIGS. 2B and 2D) respectively.

FIG. 8 illustrates a schematic cross-sectional view of a backlightmodule according to another embodiment of the invention. Referring toboth FIGS. 7A and 8, the backlight module 400 a is approximately thesame as the backlight module 400. The difference is that the backlightmodule 400 a further includes a lens 470 disposed on a light-emittingpath of the light source 440 so as to control an emitting direction ofthe light A from the light source 440.

FIG. 9 illustrates a schematic cross-sectional view of a backlightmodule according to yet another embodiment of the invention. Referringto FIGS. 7A and 9, a backlight module 400 b is approximately the same asthe backlight module 400. The difference is that the backlight module400 b further includes a transparent support plate 490 disposed betweenthe selective reflection sheet 420 and the support 430 so as to increasethe strength of the backlight module 400 b. The transparent supportplate 490 is especially suitable for large-sized backlight modules. Thetransparent support plate 490 is fabricated using, for example, atransparent acrylic plate or other transparent materials.

It should be noted that the present invention does not limit the lightsource 440 (referring to FIG. 7A) to be disposed on the edge of thereflection sheet 410 (as in the side incident type backlight module). Instill another embodiment of the invention, as shown in FIG. 10, a lightsource 440 a of a backlight module 400 c includes a plurality oflight-emitting elements 442 evenly distributed on the reflection sheet410 (as in the direct type backlight module). In the embodiment as shownin FIG. 10, a total area of the transparent regions 422 per unit areaincreases, preferably gradually, as the transparent regions are fartheraway from the light-emitting elements 442. Each light-emitting element442 is, for example, an LED or a cold cathode fluorescent lamp.

The backlight modules 400-400 c in the embodiments are the backlightmodules without a light guide plate, and they have the same advantagesas the backlight modules 300-300 c, respectively.

FIG. 11 illustrates a schematic view of an LCD according to oneembodiment of the invention. Referring to FIG. 11, an LCD 500 of theembodiment includes an LCD panel 510 and a backlight module 520 disposedunder the LCD panel 510. The backlight module 520 may be one of thebacklight modules 300-300 c and 400-400 c in the aforementionedembodiments or it may be any other backlight module having thecharacteristics of the invention. Additionally, the backlight module 520is disposed with its light-emitting direction towards the LCD panel 510,which means a surface source is provided by the backlight module 520 atits top side adjacent to the LCD panel 510. If the LCD panel 510 isflexible, the whole LCD 500 becomes flexible, too.

FIG. 12 illustrates a schematic view of an LCD according to anotherembodiment of the invention. Referring to FIGS. 11 and 12, an LCD 500 ais approximately the same as the LCD 500. The difference is that the LCD500 a further includes a first polarizer 530 and a second polarizer 540.The first polarizer 530 is disposed between the backlight module 520 andthe LCD panel 510, whereas the second polarizer 540 is disposed on theLCD panel 510. After passing through the first polarizer 530 and thesecond polarizer 540 respectively, linear polarization directions oflight are perpendicular to each other. If the light provided by thebacklight module 520 is linear polarizing light, the second polarizer540 may be removed. The first polarizer 530 and the second polarizer 540are suitable for LCD panels whose bright or dark state is determined bywhether linear polarizing light passes through or not.

In conclusion, the backlight module of disclosed embodiments of thepresent invention adopts either the combination of a reflection sheet, areflective type polarizer and a retarder or the combination of areflection sheet and a selective reflection sheet so as to generate asurface source of uniform luminance, and no light guide plate ordiffusion plate is required. Therefore, the backlight module ofdisclosed embodiments of the invention has the advantages of havingthinner thickness and lighter weight. Moreover, the backlight module ofdisclosed embodiments of the invention does not include any elementsthat are difficult to warp, such as a light guide plate or a diffusionplate, so that it can be easily designed as a flexible type backlightmodule. Further, the shapes of the through holes in the films aredesigned as such that the backlight module of disclosed embodiments ofthe invention can have better flexibility and, at the same time, thefilms can still be solidly fastened. Besides, the backlight module ofdisclosed embodiments of the invention may also be applied in LCDs, andif combined with a flexible LCD panel, would advantageously result in aflexible LCD. In addition, when the backlight module of disclosedembodiments of the invention is applied to large-sized LCDs, since thebacklight module does not have a light guide plate, the problems of lowyield rate and tendency to warping in large-sized light guide plates canbe avoided.

Although the present invention has been disclosed above by the preferredembodiments, they are not intended to limit the present invention.Anybody skilled in the art can make some modifications and alterationswithout departing from the spirit and scope of the present invention asdefined in the appended claims.

1. A backlight module, comprising: a reflection sheet; a firstreflective type polarizer disposed above the reflection sheet with a gaptherebetween; a light source disposed in said gap between the reflectionsheet and the first reflective type polarizer to provide light; aretarder disposed on the first reflective type polarizer, the retarderhaving a plurality of retarding regions and a non-retarding region; anda second reflective type polarizer disposed on the retarder, wherein thelight provided by the light source penetrating the second reflectivetype polarizer through the functioning of the retarding regions.
 2. Thebacklight module of claim 1, wherein the first reflective type polarizerand the second reflective type polarizer are linear polarizers, and alinear polarization direction of the first reflective type polarizer anda linear polarization direction of a light passing the second reflectivetype polarizer are perpendicular to each other.
 3. The backlight moduleof claim 1, wherein the first reflective type polarizer and the secondreflective type polarizer are circular polarizers, and a circularpolarization direction of the first reflective type polarizer and acircular polarization direction of the second reflective type polarizerare opposite to each other.
 4. The backlight module of claim 3, furthercomprising a ¼ wavelength retarder disposed on the second reflectivetype polarizer.
 5. The backlight module of claim 1, being a sideincident type backlight module wherein the light source is located alongan edge of the reflection sheet and emits light towards a central regionof the reflection sheet.
 6. The backlight module of claim 5, furthercomprising a lens disposed on a light-emitting path of the light source.7. The backlight module of claim 1, being a direct type backlight modulewherein the light source comprises a plurality of light-emittingelements evenly distributed on the reflection sheet.
 8. The backlightmodule of claim 1, further comprising a plurality of fasteners forfixing relative positions of the reflection sheet, the first reflectivetype polarizer, the retarder and the second reflective polarizer.
 9. Thebacklight module of claim 8, wherein the reflection sheet, the firstreflective type polarizer, the retarder and the second reflective typepolarizer have a plurality of through holes respectively, the fastenersrunning through the through holes to fasten the reflection sheet, thefirst reflective type polarizer, the retarder and the second reflectivetype polarizer, a largest dimension of at least one of the through holesbeing larger than a largest external diameter of the respectivefasteners.
 10. The backlight module of claim 9, wherein the reflectionsheet, the first reflective type polarizer, the retarder and the secondreflective type polarizer are flexible.
 11. The backlight module ofclaim 1, further comprising a support disposed between the reflectionsheet and the first reflective type polarizer to maintain the gap. 12.The backlight module of claim 11, further comprising a transparentsupport plate disposed between the first reflective type polarizer andthe support.
 13. The backlight module of claim 1, wherein the retarderis a ½ wavelength retarder.
 14. The backlight module of claim 1, whereina total area of the retarding regions per unit area of the retarderincreases as the retarding regions are farther away from the lightsource.
 15. A backlight module, comprising: a reflection sheet; aselective reflection sheet disposed above the reflection sheet with agap therebetween, the selective reflection sheet having a plurality oftransparent regions and a reflective region; and a light source disposedin the gap between the reflection sheet and the selective reflectionsheet so as to provide light.
 16. The backlight module of claim 15,wherein a total area of the transparent regions per unit area of theselective reflection sheet increases as the transparent regions arefarther away from the light source.
 17. A liquid crystal display (LCD),comprising: an LCD panel; and a backlight module as defined in claim 1.18. The LCD of claim 17, further comprising: a first polarizer disposedbetween the backlight module and the LCD panel; and a second polarizerdisposed on the LCD panel, wherein linear polarization directions of thefirst polarizer and the second polarizer are perpendicular to eachother.
 19. An LCD, comprising: an LCD panel; and a backlight module asdefined in claim
 15. 20. The LCD of claim 19, further comprising: afirst polarizer disposed between the backlight module and the LCD panel;and a second polarizer disposed on the LCD panel, wherein linearpolarization directions of the first polarizer and the second polarizerare perpendicular to each other.
 21. A backlight module, comprising: areflection sheet; a film structure disposed above the reflection sheetwith a gap therebetween; and a light source disposed in the gap betweenthe reflection sheet and the film structure so as to provide light;wherein the film structure comprises a first region for reflecting lightincident thereupon from the light source and the reflection sheet; and aplurality of second regions for transmitting at least partially lightincident thereupon from the light source and the reflection sheet. 22.The backlight module of claim 21, wherein a total area of the secondregions per unit area of the film structure increases as the secondregions are farther away from the light source.
 23. The backlight moduleof claim 22, being a side incident type backlight module wherein thelight source is located along an edge of the reflection sheet and emitslight towards a central region of the reflection sheet; and the secondregions are distributed on the film structure such that a surface sourcewith uniform luminance is provided at a top side of the film structure.24. An LCD, comprising an LCD panel and a backlight module as defined inclaim 21.